1. Field of the Invention
The present invention relates generally to wireless telecommunication systems, and in particular relates to the use of a holographic optical element (HOE) device in an optical wireless telecommunication system receiver, with the HOE device having a substantially solid form.
2. Background Information
With the increasing popularity of wide area networks, such as the Internet and/or World Wide Web, network growth and traffic have exploded in recent years. Network users continue to demand faster networks, and as network demands continue to increase, existing network infrastructures and technologies are reaching their limits.
An alternative to existing hardwire or fiber network solutions is the use of wireless optical telecommunications technology. Wireless optical telecommunications utilize beams of light as optical communications signals, and therefore do not require the routing of cables or fibers between locations. Data or information is encoded into a beam of light, and then transmitted through free space from a transmitter to a receiver.
A hindrance in the widespread acceptance and use of wireless optical telecommunications systems is the complicated, bulky, and obtrusive equipment required for reception of the optical communications signals. Most receivers used in wireless optical communications systems utilize light collection devices. These light collection devices can be simple telescopes (such as a telescope having a Schmidt configuration), or they can be more complex variations on the telescope theme. The shared element between all of these systems is that the receivers must incorporate a separation length between the light collection elements and the receive components due to the physical focal length requirements of the receiver, even when the light path is shortened using folding techniques. This separation length is typically free space, which results in a bulky and fragile receiver.
Accordingly, improvements in receivers for wireless optical telecommunication systems are needed.
According to an aspect of the invention, an apparatus has a first element having first and second surfaces, with the first surface being positionable to face incident light rays. An emulsion material is disposed over the second surface of the first element and has an interference pattern recorded thereon. A second element overlies the emulsion material and is structured to pass resulting light rays derived from the incident light rays and diffracted from the recorded interference pattern. A plurality of reflective elements are positioned adjacent to the first and second elements to fold the resulting light rays within the second element.